Electric machines that can receive high outputs as generators and/or provide high outputs as engines are used for many applications. For example, corresponding electric machines in motor vehicles are used as a part of hybrid drive, or as a drive machine with a purely electric drive. If a high output density is to be achieved, it may be necessary to cool the electric machine. A number of approaches are known that can be used for this purpose, for example cooling of the stator of the electric machine with a cooling jacket, which can be for example designed so that a water stream passes through it in order to cool the stator of the electric machine.
In particular in the case of asynchronous machines, it is possible that the rotor of the electric machine will heat up strongly. If the rotor is cooled only by the ambient air, which is to say for example via the air gap between the rotor and the stator and/or the front surfaces of the rotor, sufficient cooling, in particular cooling of the inner region of the rotor, can be often achieved only to a limited extent.